Selector arrangement for seismic prospecting system



March 25, 1952 K. w. McLoAD SELECTOR ARRANGEMENT FOR SEISMIC PROSPECTINGSYSTEM Filed MaIGh l0, 1948 9 Sheets-Sheet l OR LOAD K. Wi MGLOAD March25, 1952 SELECTOR ARRANGEMENT FOR SEISMIC PROSPECT-ING SYSTEM 9Sheets-Sheet 2 Filed March 10, 1948 INVENTOR KENNETH W M'= LOAD BYl 2March 25, 1952 K.vw. McLoAD y 2,590,531

SELECTOR ARRANGEMENT FOR SEISMIOPROSPECTING SYSTEM Filed March 10, 19489 She'ts-She'et. 3

INVENTOR KENNETH W. Mc LOAD y 'MM5/Wi March 25, 1952 K. w. MCLOAD-2590531' SELECTOR ARRANGEMENT Foa sEIsMIc PRosPEcTING` SYSTEM FiledMarch 1o, 1948 sheets-sheet 4 iQ 2 7a. w/ 2a' 70 I l l n 27 275 7/ 6668a.

3 /A/s//LAT/OA/ 72 "Figi,

mvEN'QR .A 1 KENNETH W. MLOAD March 25, 1952 K. w. MGLOAD SELECTORARRANGEMENT FQB SEI'SMICYJPROSPECTING SYSTEM 9 Sheng-sheet 5 Filed March1o," 1948 A INVENTOR K NNETH W. Mc LOAD BY Jil.

aucun/ i March 25, 1952 l K. 1w. MGLQAD 2,590,531

S!ZZI..,}."1G'I.`C)R ARRANGEMENT FOR SEISMI-C PROSPECTING SYSTEM FiledMarch 10, 1948 9 Sheets-Sheet 6 INVENTR 29 n NNETH w. Mc LOAD TlH-- BY@MMU March 25, 1952 K. w. MQLoAD SELECTOR ARRANGEMENT FOR sEIsMIcPRosPEcTm sYsTEM Fiied March 1o, 1948 9 Sheets-sheet 7 INVENTOR KENNETHW. M LOAD www@ flor/nw March 25, 1952 K. W. MCLQAD 2590531 i sELEoToRARRANGEMENT FOR sEIsMIc PRosPETING SYSTEMv Filed March 10. 1948 9.'Sheets-#Sheet 8 mvENTpR ENNETH w. M LOAD March 25, 1952 K. w. MGLOAD2,590,53

SELECTOR ARRANGEMENT FOR SEISMIC PROSPECTING SYSTEM i Filed MaICh l0,1948 SheeitS-Shet 9 INVENTOR KENNETH W. Mc LOAD Patented Mar. 25, 1952UNITED STATES SELECTOR ARRANGEMENT FOR SEISMIC PROSPECTING SYSTEMKenneth W. McLoad, Dallas, Tex., assigner, by

mesne assignments, to

Socony-Vacuum il Company, Incorporated, New York, N. Y., a corporationof New York Application March 10, 1948, Serial No. 14,115

9 Claims.

This invention relates to geophysical prospecting and more particularlyto seismic surveying in areas covered by water, as over coastal areas,and has for an object the provision of a method and apparatus tofacilitate carrying on such surveys in a minimum of time and duringrough weather conditions that would otherwise necessitate cessation ofoperations.

Due to the generally accepted belief and the knowledge that there aresubstantial oil or petroleum deposits in coastal areas covered by water,it has become most desirable to conduct seismic surveys for sub-surfacemapping of such areas in order to locate characteristic sub-surfaceformations which provide the most likely locations for the drilling ofwells.

The diiiiculties encountered in conducting seismic surveys in submergedareas will be apparent when it is considered that seismic detectors mustbe placed along a predetermined line at predetermined intervals andoriented in a predetermined position at each location along that line.The geophones comprising a spread, in conformance to techniques used onland, are usually located at regularly spaced points along the line andmust be oriented in such a position, usually vertical, that theinstantaneous voltage of a geophone will be of the proper polarity withrespect to the seismic waves to be recorded and of the same polarity asthe other geophones of the spread. Further, a spread of geophones, asused in present day seismograph practice to produce a record, comprisesat least two geophones per trace although it is often preferable toutilize a number greater than this in order to eliminate near-surfaceeffects. This means that the spread, in orde:` to produce a usefulrecord of six or seven traces, will comprise twelve, fourteen, or moregeophones, each of which must be positioned at predetermined locationswith respect to a line along which the seismic survey is beingconducted.

Further, it is necessary to provide geophones in which the operatingparts are fluid sealed, a pair of insulated conductors extending fromeach geovphone to the associated recording instruments,

and some means and/or method by which each of the geophones may beplaced at some predetermined point in or on the water in such a positiontha-t the geophones will be sensitive to the seismic waves to berecorded.

There have been several different approaches to the problem. Three ofthe suggested solutions are characterized respectively by (l) mountingeach geophone in a separate float or boat; (2) suspending each geophonefrom buoys on a lowfrequency system at some intermediate depth; and (3)providing means whereby the geophones, upon removal of a towing forcewill descend to, and rest upon, the ocean floor.

The desirability of having a plurality of geophones comprising a spreadand their associated conductors so arranged that they may be towed fromone location to another has been recognized. However, in such systemsthe electrical conductors connecting each of the geophones in the spreadto recording apparatus in a towing unit must be sealed or provided witha water-tight insulating arrangement in order to prevent shortcircuitingof the conducting paths by the entrance of Water. At the same time,provision must be made for repairs in event of failure of any of thedetector units or of the circuits of the system.

Further, in seismic prospecting it is often desirable that signals fromtwo or more geophones in a spread' may be mixed by providing a commonconducting path from each of such geophones to the recordinginstruments. A system having a maximum degree of flexibility is one inwhich any of the detector units of the spread may readily be connectedto any other detector and to the recorder. The present invention, in oneform thereof, provides means for readily assembling geophones and cableunits to form a spread in which any desired inter-mixing of thegeophones may be effected. Connections are made in such a manner thatthe possibility of the circuits becoming shorted at the point ofconnection is eliminated. More particularly, a plurality of cablesections and geophones designed to be connected together in end-to-endrelation are provided with terminal members, preferably in such arraythat contact is made in the electrical circuits as the mechanicalconnection is made between lcable sections and the geophone housings.The terminal members, which may be jacks and plugs preferably aresymmetrically disposed lwith respect to the axis of the cablesectionsand the geophone housings. With such symmetry the geophones maybe assembled to the cable sections in any one of a plurality ofdifferent angular positions, thereby selectively to connect any onegeophone element to any one of a plurality of pairs of -conductors inthe cable sections.

The present invention is primarily directed to the cable-selectorarrangement by means of which geophones may be connected in any desiredcircuit leading to the recorder. The broader aspects of the system withwhich the present invention is illustrated forms the subject matter ofan application filed concurrently herewith by Goethe M. Groenendyke,Serial No. 14,027, and assigned to the same assignee as the presentapplication,

For further objects and advantages of the invention, reference shall nowbe had to the following description taken in conjunction with thedrawings in which:

Fig. 1 is a sectional view of a submerged area illustrating an underwater surveying apparatus utilizing the present invention.

Fig. 2 is a sectional elevation of a part of the apparatus in Fig. 1including a portion of the cable connector assembly with all but two ofthe electrical conductors being omitted; y

Fig. 3 is an exploded View of a gimbal mounting provided for thedetector unit of the system of Fig. l;

Fig. 4 is a sectional View of the construction of the cable connectorassembly at the left of Fig. 2;

Fig. 5 is a sectional view of a modied form of a cable connectorassembly;

Fig. 6 is a sectional view of Fig. 2 taken along line 6 6;

Fig. 7 is a sectional View of Fig. 2 taken along line 1 1;

Fig. 8 is an enlarged sectional View ofthe left end of geophone housingand the cable connector assembly of Fig. 2 illustrating the manner inwhich the electrical connections are made between the cable sections andgeophone housings.

Fig. 9 is a perspective view of circuit connectors in a geophone caseand on the cooperating end assembly of a length of cable.

Fig. 10 is a modied form of apparatus of Fig. 1;

Fig. l1 diagrammatically illustrates the cable of Fig. 10 showing oneway in which the geophones may be connected;

Fig. 12 is an enlarged view of a section of the right end of thoseportions of the cable which house geophones I9 and ISA;

Fig. 13 is an enlarged view of a section of the left end of thoseportions of the cable which house geophones I9 and ISA;

Fig. 14 is an enlarged view of the righthand end of geophones I4 and IA;

Fig. l5 is an enlarged view of a portion of the lefthand end ofgeophones I4 and IIIA; and

Fig. i6 is a perspective view of the geophone unit of Fig. 2 mounted ina double gimbal arrangement.

Referring to the drawings, there has been illustrated in Fig. 1 aseismic surveying apparatus utilizing the invention in an area coveredby water in which a seismic survey is to be conducted. As shown in thedrawings the surveying apparatus and the associated vessels or boats areanchored in suitable positions. More specifically, the recording boat I0is anchored, although the anchor is not illustrated, in a position inadvance of the shooting boat I I. From the recording boat I thereextends that part of the seismic surveying apparatus with which thepresent invention is concerned; more specically, there extends from theboat I a cable which, as more fully explained hereinafter, includestension elements to give to the cable adequate strength to withstand themaximum tensional forces capable of development by the boat I El, andthe electrical conductors which complete electrical circuits to thegeophones which comprise the spread. Seven geophone units or assembliesS-IS are shown in Fig. l, although it is to be understood that thespread may consist of any desired number of geophone units such as thepreviously mentioned twelve, fourteen, or more units. For the purposesof clarity and simplicity in the explanation of one adaptation of theinvention the simple 'Y-geophone spread has been illustrated. For thesame reason, it will be assumed in the following description that thesignals from these seven geophones I3-I9 are to be transmitted unmixedto the recording instruments carried by boat I 0 where the signals willbe recorded on six or seven traces.

As is well understood by those skilled in the art, seismic surveying maybe conducted by positioning the geophones comprising the spread atpredetermined locations along a line, ordinarily straight, over whichthe survey is to be made. With the geophones positioned as in Fig. l, acharge of dynamite suitably located with respect to the spread isdetonated to generate seismic waves. Where the survey is to be conductedin areas covered by water, it becomes feasible to lower from theshooting boat I! a charge 20 of dynamite to the underwater bed orbottom, the weight of the water itself providing the necessary tamping.VUpon exchange of proper signals between the recording boat IG and theshooting boat I I, the charge of dynamite 20 is detonated to generatethe seismic waves which thereupon travel downwardly through the earth.Upon reaching an interface or boundary of two sub-surface strata ofdiffering properties, a part of the seismic energy is reflected. Thepaths of energy traveling to and reflected from the interface 2l havebeen indicated by the lines 22, while the travel paths of energytraveling to and reflected from the interface 23 have been indicated bythe lines 24. As the reflected energy arrives at the geophones IB-IS,seismic signals are generated by each geophone which are transmitted tothe recorder by way of the conductors included in the cable I2. The timerequired after the detonation of the charge of dynamite 2D until thecompletion of the recording period is of the order of a few seconds.Since this time is so short, it will be readily understood that there isgreat economic value to provide a system which will reduce the timerequired to arrange the equipment in preparation for succeeding shots land subsequent recording periods. More specically, after the detonationof the charge 20 the shooting boat II moves to a position in advance ofthe recording boat I0, and at a predetermined location there is loweredto the underwater floor or bottom a further charge of dynamite whichwill be detonated and further seismic records made. While the shootingboat II remains at its new location, the recording boat I0 will thenmove forward, towing and dragging the surveying equipment forming a partof the cable I2 after it until a new and predetermined position isreached. All geophones are at all times properly spaced, properlyoriented and when stationary are immediately ready to receive seismicsignals for the recording of data resulting from the detonation ofsucceeding charges from the shooting boat II in its new position. Fromthe foregoing description of a surveying apparatus to be used insubmerged areas, it will be readily apparent that the apparatus embodiesfeatures substantially different from apparatus used in land surveys. Ifthe cable is to be towed from one spread to another, it must berelatively smooth and streamlined in order to minimize the possibilityof becoming entangled with underwater obstructions.

In the present invention means are provided for connecting the cablesections and the geophones in such a relatively smooth, streamlinedunit. The electrical paths over which signals from the geophones may beconducted through the cable sections to the recording apparatus on boatare completed through each of the geophone housings, such as the housing29 of Fig. 2,

in a manner which conforms to the aforementioned requirement of arelatively smooth streamlined unit. At the same time the area in whichconnections are made is sealed to prevent entry of moisture or waterthereinto,` thus preventing a snorting of the circuits. The connectionsare so arranged on cooperating units that by rotation of a cable sectionabout its longitudinal axis with respect to the adjacent geophone or thegeophone to be connected thereto, signals generated in that particulargeophone may be transmitted over any one of a plurality of pairs ofconductors in the cable I2. With the foregoing general understanding ofone application of the invention and the manner in which it operates,reference will now be had to the detailed drawings, particularly Fig. 2which is a sectional view of that part of the cable I2 which includesthe electrical connections between cable sections and geophone assemblyor geophone unit I4.

Referring to Fig. 2, section [5B of the cable l2 between the geophoneassembly I4 and the assembly i5 has been terminated at the right of Fig.2 in a plug housing or closure member 21, which is shown in detail inFig. 5. The plug housing, as shown in both Figs. 2 and 5, is providedwith a flange 21a which, by means of a series of bolts 28, is attachedto a flange face of the housing 29 in which a seismic wave detector orgeophone 30, Fig. 2 is mounted. The housing 29 is provided with anopening, best shown in Fig. 9, through which parts may be introduced inconstruction. A lid 29a is fastened to the case 29 by bolts 29h withgasket 29C effecting a watertight seal as shown in Figs. 2, 6 and 7. Toprovide a watertight seal at the junction of plug 21 and the ends ofhousing 29, a gasket 3l is provided between the flange face of housing29 and the flange 21a. The electrical conductors are carried in aninsulating jacket or cable 32 which may be of rubber or other suitableflexible insulating material. In Fig. 2 only eight of the fourteen leadwires or conductors of cable 32 appear, two of them, the conductors 33and 34, serve to complete connections to the detector or geophone 30. Amore detailed discussion of the manner in which the remaining conductorsextend through the housing 29 will be later referred to, particularly inconnection with Figs. 6-9.

The Vconductors 33 and 34 are connected to plugs 35 and 36 carried byand supported from a ring 31 of electrical insulating material which isitself secured to the plug housing 21 by means of screws 38. Plugs 35and 36 are illustrated as nesting within and making good electricalcontact with jacks 40a and 401) carried in an electrical insulatingmember 39 fastened in the end of housing 29 by spring 39a. From the jack49h a conductor 42 is electrically connected to a rectangular shank of aspring-biased contact plunger 43 supported in a flanged cylinder 44which is attached to a bea-ring support 45 of insulating material, as byScrews 46. A spring 41 within the closed end of the cylinder` 44 urgesthe contact plunger 43 against a butt contact 48 carried in aninsulating member 49. From the contact 48 connection is made byconductor 50 to the sensitive element of the detector or geophone 30.Connection to the other terminal of geophone 3D is by way of conductor5I and through a like assembly including a butt contact 52 and aspring-biased contact plunger 53 and thence by conductor 54 to a jack55a and to `a plug 56 to which is connected a conductor 5 1 of sectionI4B of the cable I2.

It will be observed in Fig. 1 that each geophone unit or assembly formsin the cable I2 a bulge or enlargement, but not one either of length orof diameter too great to prevent the handling of the cable as a whole asby a reeling drum or the like. Notwithstanding the compactness of thegeophone assembly, there are incorporated therein provisions forassuring that the detector unit or geophone 30 will always be in aposition for the most favorable reception of seismic signals. Indragging or towing the cable I2 along the bottom of the submerged areabeing explored, the cable may tend to turn about on its longitudinalaxis. It is provided, however, that each detecting unit will remainoriented and will be maintained in a vertical position. Referring toFig. 2 and the exploded View Fig. 3, this is accomplished by supportingthe geophone unit 30 in a cradle 58, the lower end of which, as viewedin Figs. 2 and 3, is of heavy construction to position well below theaxis of rotation of shafts 62 and 63 the center o f gravity of theassembly, thus to impart to the geophone 30 and the cradle 58 a stronggravity bias which, in the manner of a pendulum, maintains the geophone39 in a vertical position. Preferably, the cradle 58 is supported byanti-friction bearings, illustrated as ball bearingV assemblies 6I! and6I, the assembly 60 being carried by bearing support 45 of insulatingmaterial, while the bearing 6I is carried by the insulating support 45a.The supports 45 and 45a are mounted on angular ribs 59 by bolts 59a, asshown in Fig. 6.

It will be observed the cradle 53 is provided with cylindricalextensions or center-bored shafts 62 and 63 which are pressed into theinner race of the respective ball bearing assemblies 69 and 6I. eachcylindrical extension having pressed therein an insulating bushing, suchas the bushing 49 for the contact 48. It is to be further observed thatthe axis of the cylindrical extensions or stub-shafts 62 and 53 is inline with, or coaxial of, the cable I2. The seismic detector or geophone30 is provided with its own housing, generally hermetically sealed (Fig.11) with terminals extending therefrom for connection to the conductors50 and 5I of Fig. 2. The cradle 58, as best shown in Fig. 3, isgenerally cylindrical in shape, closed at the bottom and has an innerdiameter of a length to receive therein the housing of the geophone 30.In the form illustrated the lower end of the geophone 30 has one end 39aof reduced cross-section, and the' cable 58 is provided with are-entrant opening 58a which serves to form a seating ledge for thelarger diameter section of the geophone housings; The geophone isclamped into the cradle by means of a fiber clamping member 64 throughwhich there extend clamping bolts 65, Figs. 3, 6 and 7.

It is quite apparent from Figs. 2, 3, 6 and 7 that since most of themass of the heavy brass cradle and geophone assembly is below thepivotal axis, the position of the center of gravity is well below thataxis, thus capable of developing considerable torque. Since thespring-biased friction contacts are small in area and effective at ashort radius, the frictional torque or drag caused thereby is negligibleand the geophone 30 will always take a position with its longitudinalaxis vertical, regardless of rotation of the cable and housing abouttheir common longitudinal axis. This automatic positioning of eachgeophone 39 occurs even though the geophone housing 29 may not itself behorizontal. Thus, as shown in Fig. 1, all of the geophones are more orless inclined to the horizontal with the exception of geophones I3, I5and I8. Nevertheless, in all of the remaining geophone units eachgeophone ordetector will be positioned by its own cradle so that it isgenerally vertical, and in all cases each geophone responds to thearrival of seismic waves with the same polarity as every other geophone.

The detector or geophone 30 may itself be of any suitable type,depending upon the character of the survey undertaken and the type ordesign of recording equipment with which it is used. For example, it maybe of a well known velocity type such as the one illustrated in Fig. 11.However, either the displacement, velocity or acceleration type may beutilized as the vibration-sensitive device or seismic detector 30.

With the foregoing understanding of the construction and arrangement ofthe parts within the geophone unit or assembly I, it will be understoodthat each of the remaining assemblies I3 and I5--I 9 is similarlyconstructed. The present invention provides that all of the electricalconductors extend throughout thelength of cable I2 and from the rear ofthe boat I to the recording instruments carried therein. In Fig. 2 onlyeight of the multiple conductors of the cable appear, two of which, theconductors 42a and 54a, extend through the case 29. For a seven-geophonespread, there will be at least fourteen separate conductors, eachinsulated from the other and extending the full length of the cable fromthe boat I0 to the geophone assembly I3. While it would be possible toterminate two conductors in the assembly I9, to terminate two additionalconductors in the assembly I8, etc., to the last assembly I3, it ispreferred to have all conductors extend through the entire cable. rlhus,all of the intermediate sections of cable respectively disposed betweenadjacent geophone assemblies are of like construction. Similarly, eachgeophone assembly is of like construction, which means that anyparticular section may be removed and another like section substitutedtherefor. If greater spacings are desired between adjacent geophones,longer interconnecting cables are substituted for the shorter ones.

Thus, the interchangeability and flexibility ail'orded adapts thesurveying apparatus as a whole to any conditions which may beencountered in the field and imparts to it the same degree offlexibility that is had with equipment of the type previously used onland. As has heretofore been mentioned, the cable I2 includes as anintegral part thereof an inner electrical cableyhich consists of theelectrical conductors embedded or implanted in the continuous rubberjacket 32. In the form of the cable shown in Fig. 5 the electrical cable32 has wound about it a plurality of wire ropes 66. The wire-wrappedcable has an outer cover 61 of abrasion-resistant material such asfabric reinforced rubber, either natural or synthetic. The covering 6lis terminated at the juncture of each cable section and geophoneassembly, as at a barbed end of the fitting E8, a plurality of turns ofwire 6 being effective tightly to hold the outer cover SI in piace. Thewire ropes 66 extend inwardly through the fitting 68 and terminate at aring 'I to which they are suitably secured as by soldering, spotwelding,or the like. The lefthand end of the fitting 68, as viewed in Fig. 5, isthreaded into an extension of the plug housing 21. Between a shoulder2lb of the plug housing and the tapered inner `surface 68a is a wedgingmember 1I, the lefthand end of which abuts against shoulder 2lb.Preferably the fitting 68 in the region indicated by the referencecharacter 'I2 is made hexagonal or square to receive a wrench or othertool tightly to force the fitting 68 into the plug housing 2l'. Whenthis is done, the wedge 'II .is driven tightly against the wire ropesS6. In this manner the wire ropes 6B are firmly and frictionallyconnected to the plug housing 27 which, it will be remembered, is inturn bolted to the housing 28 of the geophone assembly I4. With thisconstruction, as each cable section enters a geophone assembly, there isa divorcement between the tension members and the electrical members,the latter thereby being protected against application thereto of anytowing forces applied to the tension members of the cable by boat I.While it is intended that the cable at the barbed end of each of thefittings 68 will be watertight to prevent ingress of seawater,additional protection is provided for the electrical circuits in thegeophone and plug assemblies by the provision of a plurality of sealingmembers 13 shown in the form of rubber washers. They are disposedcentrally of the plug housing 27 between the metallic washers 13a. Whencompressed by a nut or compression member 'I4 which threadedly engagesthe housing 21, the rubber washers 'I3 expand to form, with theelectrical cable 32 and with the plug housing 21, a wholly watertightseal.

While the form of cable and cable connector shown in Fig. 5 is preferredand may be utilized on each end of each cable section, other forms maybe, and have been, utilized. For example, the cable connector shown inFig. 4 has been found satisfactory and is of the type which may bereadily fabricated without special equipment s is required for theassembly of Fig. 5. To minimize the number of drawings, the arrangementof Fig. 5 has been shown on the righthand side of Fig. 2, while theassembly of Fig. 4 has been shown on the lefthand side of Fig. 2.

Referring now to Figs. 2 and 4, the towing forces are transmitted fromthe housing 29 through a plurality cf bolts 28 to the lefthand plughousing 21. In this case, insulated electrical conductors 'I6 are moldedor vulcanized into a plug 'I1 of rubber or the like which, with thesealing members 'I3 and 13a and the nut or compression member '54, formsa watertight connection. In the form of the cable of Fig. 4, theconductors 'I6 extend through the outer cover 67 together with a braidedwire cable 18. The cable 'IB is terminated within a wedging member whichrests within a fitting 8l and against a shoulder Sla thereof. Thewedging member 80 has a tapered socket through which the end of thecable 'i3 extends. The end of the cable 'I8 is held in place by thewedge 82 which is shown as welded or brazed to the cable 18. Preferably,before the brazing operation the strands of cable 'I8 are spreadoutwardly, and in the brazing or soldering operation they are integratedinto a mass to form the wedge-shaped end 82 Whose configuration iscomplementary to that of the tapered socket of member 8B. Any tensionalforce exerted on the cable 'ill tends to press the wedge-shaped end 82and the wedging member 80 more firmly together. The provision of someslack in the wires 'I5 as they enter plug 'Il insures that the wireswill not be subject to tensional forces. Thus, from the plug housing 21,the towing forces are transmitted through the threaded end 8Ib of themember `8| and thence through wedging member 89 to the wedgething beingthat in any particular surveying equipment all plug assemblies shall beof such uniform construction as will provide interchangeability.

With either cable arrangement of Fig. 4 or Fig. 5, a towing force of anydesired magnitude may be applied to the several geophone assemblieswithout exertion of forces on the electrical cables, and thus thesurveying equipment may be moved readily and quickly from one locationto another.

There has already been mentioned the fact that the electrical circuitsare continuous from one end of the cable to the other. The manner inwhich the electrical conductors are continued through the cable has beenillustrated with particular reference to the conductors 42a, and 54a ofFig. 2 and is best shown in Figs 8 and 9. In Fig. 8, which is anenlarged sectional elevation of the lefthand plug and jack assembly ofFig. 2 there is shown in detail the manner in which the conductors areattached to the jacks carried in the insulating member or disc 39. At amounting clamp 83 the individual conductors are separated and eachindividual wire is connected to one of the jacks carried by theinsulated disc 39.

The two insulating discs 39 located at the right and the left of eachgeophone assembly, as viewed in Fig. 2, are of identical construction,and the wires or conductors extend therebetween to like locations; thatis to say, the same conductor will be connected to the lower-most jack,i. e., 40a and 55a, in the t'wo discs 39 at the opposite ends of eachassembly. As shown in Figs. 6 and '7 and in the exploded View of Fig. 9,the conductors including 62a and 54a may be laid side by side againstthe inner wall of the housing 29 and held there as by clamps 83 of Fig.8. 'Ihe six conductors which appear in the right of Figs. 6 and 7 appearin Fig. 9 in the cutaway section. In the embodiment of the inventionillustrated, and as previously described, the detector or geophone 30 iselectrically connected by conductor 50, contact assembly 48, 43, and byconductor 42 to the jack llllb at the righthand end of Fig. 2; and byconductor 5 I, contact assembly 52, 53 and by conductor 54 to the jack55a at the lefthand end of Fig. 2. The jack 49h is connected by theconductor 42a to the jack 5517. Similarly the jack 55a and the jack 40aare interconnected by conductor 54a. It is to be understood that thejacks 40a and 40h are located in the supporting disc (not shown) locatedat the righthand end of Fig. 9 in the same radial positions ascorresponding jacks .55a and 55h carried by disc 39. In like manner theremaining jacks at the respective ends of the housing 29 areinterconnected so that electrical circuits extend between each pair ofsimilarly located jacks. It will be understood that the particularconstruction of plug and jack assemblies shown may be modified orvaried, though the system shown is the best form in which the inventionhas been used.

In the exploded view of Fig. 9 the geophone coil has been illustrateddiagrammatically by a dotted line and is shown connected to the jacks55a and 55h. The two plugs 56 and 86 are arranged to be received by thejacks 55a. and 55D. similarly, additional pairs of jacks and plugs serveto take care of the remaining circuits. Since the plugs and jacks aresymmetrically disposed about the axis of the assembly, the plugs may beinserted into any selected jacks, that is the plugs and their cablesection may be rotated about the longitudinal axis for movement of plugs55 and 86 into any selected pair of jacks. Preferably the sensitiveelement or geophone coil of each geophone is connected to thecorresponding jacks of each assembly. The ange 21a may then be securedin the selected position since the bolt holes in flange 27a coincidewith those of the housing 29. The advantage of this feature is that atthe factory all coils or pickup units will be connected to jacks in likeor identical positions, such, for example, as to jacks 55m-55h, 40ct-40Dof Fig. 2. Each of the pairs of jacks bears identifying characters onthe face of the disc or insulating member 39. As shown in Fig. 9, eachpair of jacks has been identied by the letters A, B, C, D, E, F, G. Theholes in the flange of housing 29 are numbered from 1 to '7, thesenumerals being stamped on the flange, preferably on the peripheral facethereof. In Fig. 9 only the numbers 6 and 7 appear on the peripheralface of the lefthand flange. For the purpose of the followingdescription the other numerals l to 5 are shown outwardly of the flangebut in positions corresponding with their stamped locations on theflange. The coils of each of the geophones will be assumed to beconnected t0 corresponding pairs of jacks. For example, the coil 85,diagrammatically shown in Fig. 9, is connected to the jacks 55a and 55h.These jacks, those nearest the numeral I, will be identied with the codemarking A. Corresponding numerals and letters appear on each geophoneassembly in like locations.

For a surveying system in which signals from each geophone are to beseparately transmitted to the recorder, the plug-contactassemblyincluding the flange 21a of each section ofthe cable will beassembled with respect to each geophone housing in a different angularposition. For this purpose each flange 27a, Fig. 9, is provided with amarker or index which may be conveniently in the form of a notch 8l.Starting with the length of cable from boat I0, Fig.1, the cable flangemay be assembled to the housing of the geophone assembly or unit I9 withits index or notch 81 in the No. I position. This will connect the coilor detecting element 85 of the unit I9 to a first pair of conductors ofthe cable 32. The righthand flange of the cable section |9B ispositioned in a like manner with its index in the No. I position of thelei'thand flange of geophone assembly I9. The lefthand ange of cablesection ISB is positioned with its index in the No. 2 position ofgeophone assembly I8, and the righthand flange of the cable section I8bis, likewise, assembled in the No. 2 position of geophone assembly I8,thus connecting the geophone coil of that assembly to a second pair ofconductors. Similarly, the iianges of cable sections I'IB, IBB, I5B andIAB are respectively associated in positions numbered 3-1 of units I1,I5, I5, I4 and I3 to connect theirV respective geophone coils toseparate pairs of conductors. The assembly of the various flanges in theforegoing manner provides a separate electrical circuit to the recordingapparatus from each coil or sensitive element of each detecting unit.

Not only has the foregoing constructionY the advantage of uniformity inthe manufacture of geophone units, but it also provides, in eldoperations, an exceedingly useful and convenient switching arrangement,since if the associated cable flanges are assembled to two geophoneunits in like positions, such as the No. I position, thc two coils ofthose units will be connected in parallel in a circuit which extends tothe recorder. Thus, in the assembly of the surveying apparatus, any twoor more geophones may be readily connected in parallel for the mixing ofsignals therefrom.

y Further to illustrate the present invention, Figs. and 11 show asystem in which the geophones are connected in pairs, the geophones ofeach pair being in parallel. In the cablefof Fig. 10 fourteen geophoneassemblies are utilized,

Yeight of which, the assemblies I3, I3A, I4, I4A,

I5, I8A, I9 and I9A,are shown. The cable is assembled with two of itsgeophones connected to each pair of its conductors. Accordingly, thelefthand anges of the cable sections 9| and 92 are bolted to geophonesI9A and I9 with their notches or indexesin the No. I positions;likewise, the righthand flanges of cable sections 92 and 93 are boltedto geophone assemblies I9A and I9 in the No. I position. In Fig. 12 afractional part of the righthand end of the geophone ISA is shown withthe cable vflange 21a assembled lwith its index 81 opposite the numeralI. Similarly, in Fig. 13 the lefthand end of geophone assembly I9A isshown with the cable flange 21a assembled with its index in the No. Iposition. The righthand end of geophone assembly I9 and its cablesection 92 will be assembled as shown in Fig. 12', while the lefthandend will be the same as shown in Fig. 13. As a further example as to howthe cable sections are assembled, reference may be had to Figs. 14 and1-5 which fractionally illustrate the associated flanges of geophoneassembly I 4A. The coil of 'geophone assembly I4A is connected inparallel with the coil of geophone assembly I4 and to conductors leadingto the jacks opposite the No. 6 position. Accordingly, the index 81 ofthe ange 21a of cable section 96 is opposite numeral 6 (which is upsidedown), and the index 81 of the flange 21a. of cable section 91 isopposite the numeral 6. Similarly, the indexes of the flanges connectedto the geophone assembly I4 are opposite the numeral 6. It willthus beseen that the desired connec-4 tions of the geophones may be readilyeffected, it being understood the remaining pairs of geophones aresimilarly connected to the remaining pairs of conductors by similarlyassembling cable sections 94-99. The geophone assembly I3 is sealed atits left end by a disc or closure I 3a.

The system of Fig. 10, as a whole, is diagrammatically illustrated inFig. 11. The coil I9b of the assembly I9A is, of course, shown connectedby conductors to a double pair of jacks identified by the letter A, onepair being at one end and the other pair at the other end of thegeophone case or housing. Similarly, the coil I9c is connected to likedouble pairs of jacks. Since the pair of plugs of the associated cablesections located in the No. I position complete the connections to coilsIElb` and |90, the signals therefrom are mixed in the circuit comprisingthe pair of conductors I. It will be observed that these conductorsextend from the recorder and boat (not shown in Fig. 11) throughout thecable including all fourteen geophone assemblies. Only coils I9b and I9care connected to the pair of conductors 20|, since all other cableflanges are dierently associated with the remaining geophone assemblies.More particularly, the cable flanges of assembly I8A are associatedtherewith, with the indexes opposite the No. 2 positions. Thus, thegeophone coil Ib is connected to the pair of conductors 202. Thegeophone itself has in this instance been shown in detail with thehousing omitted in order that the diagram as a whole may be given agreater functional meaning. To the left of that geophone the cable isshown broken away. It will be understood, however, that the nextgeophone coil will be connected to the pair of conductors 202, andadditional pairs of geophone coils to the pairs of conductors 203 and204. One geophone coil will also be connected in parallel with the coilI5c and to the pair of conductors 205. These switching or parallelingoperations are simply accomplished by successively assembling the cableassemblies with their indexes in proper relation to the numberedpositions of the anges of the geophone assemblies. Thus,lthe indexes ofthe cable flanges associated with the geophones I4A-I4, I3A-I3, will beassembled respectively in the No. 6 and No. 1 positions ofthe housingsin order to connect coils Idb and I4c to the pair of conductors 20B; andto connect coils I3b and I3c to the pair of conductors 201.

If it is desired to mix the signals from three geophones, as from coilsI8b, I9c and I9b, it is only necessary to couple the associated cablesections to the selected geophone housing with the indexes on the angesof such cable sections located opposite the No. I positions. |I'hus, anygeophone coil will be connected in parallel with any other coil if theindexes4 of the cable sections are assembled to the geophone housings inthe same numbered positions. Mixing of signals from any selected groupof geophones may readily be accomplished.

The general practice of utilizing several geophones in parallel for eachtrace is familiar to those skilled in the art and is desirable fieldpractice for the improvement of seismic records where there prevails ahigh noise level or high amplitude of spurious signals due to nearsurface effects. In some areas it has been found necessary to use ten ormore geophones per trace in order to distinguish reflections over noiseThe present invention provides means for an underwater survey and, asindicated in Fig. 10, any desired number of geophones may be paralleled.

While the geophones may be of any suitable type, a geophone of thevelocity type is shown in Fig. '11'. It comprises a magnetic structure|00 which is provided with a central pole piece IOI. A plurality ofturns of wire forming the coil Ib are wound on a spool or form |03 whichis resiliently mounted by Springs |04 axially of and complementary withthe central pole piece IOI. Coil I8b is terminated in glass-sealterminal posts |05 which extend through a hermetically sealed enclosure|06 for the assembly. This device may be taken as illustrative of one ofseveral types of geophones or vibration-sensitive devices now in use,and which may readily be adaptable to the system here-to-fore described.

In utilizing the method and apparatus of the above-described modicationof the invention, it has been found that the cable comes to rest uponthe ocean floor with the longitudinal axis sufficiently i horizontal asnot to require compensation for deviation of each geophone from thehorizontal. For applications in which corrections should be made, adouble-gimbal mounting may be utilized lso that the geophone unit itselfwill remain vertical regardless of the positionl of the geophonehousing. Such a mounting is shown in Fig. 16 wherein the bottom-heavycradle 58 of Figs. 2 and 3, with the detector'30 nested therein, ismounted on a ring IH provided with pivots H2 and H3, providing arotational axis perpendicular to, and intersecting, the pivotal axis ofthe cradle 58. More specifically, the bottom-heavy cradle 58 of Fig. '16has its anti-friction bearings 60 and 6I carried by mountings H0,forming a part of the gimbal ring IH. The ring II l is provided withpivots or shafts which are mounted in the geophone case in the samemanner as are shafts 62 and 63 in the construction of Fig. 2. Shafts 62,63, H2 and l|3 are provided with electrical paths for transferringsignals generated by geophone 30 through the axis of rotation to thejacks carried by the housing (not shown in Fig. 16). The electrical pathof the double-gimbal arrangement includes canductors 50 and 5I,insulated plug arrangement (not shown, but similar to plugs 48 and 52 ofFigs. 2 and 3), spring-biased plunger H 4, conductors I l5 andinsulatedI plug I I6, shown in section at the left of Fig. 16. H

The construction so far described is characterized by the provision ofthe interchangeable 'geophone units and the interchangeable cablesections. Such a construction embodying the features of the presentinvention eliminates many problems which would otherwise arise in theeld, provides for many contingencies, and permits a wide variety ofoperating methods to meet widely varying conditions. Such an arrangementembodying the present invention is particularly desirable for underwaterexploration, since in the course of time, it is possible that certaingeophones or cable sections may be damaged by sharp coral formations orby obstacles encountered during the towing of the spread from onelocation to another. When any unit fails or when the abrasion-resistantcovering is broken, new units or cable sections may be readilysubstituted, thus eliminating time consuming delays. The constructionpermitting the selective connections between cable sections and geophoneunits is such that the surveying apparatus is of a relativelystreamlined character. With the apparatus thus constructed, thepossibility of impalement upon, or the wedging into, sub-surfaceobstacles is minimized, the cable unit l2 being entirely free ofbranches, divisions, extensions and any unwieldly appending componentswhich would readily lodge behind and jam in under-water obstacles roughin phone in a straight line with equal spacing therebetween. There hasbeen found the further advantage that the towing of the cablegeophoneassembly from one location to the other, particularly in a sandy ormuddy bottom, embeds the cable and assemblies into the bottom, keepsthem generally horizontal, and assures e'ioient transmission of theseismic signals from the earth to the geophone housing for production ofseismic signals of amplitude higher than would be expected on dry landwith comparable conditions of operation.

Though a preferred embodiment of the invention has been disclosed indetail, it is to be understood that further modifications within thescope of the appended claims may now suggest themselves.

What is claimed is:

1. A seismic surveying apparatus in which a plurality of detectors arerespectively separated and electrically interconnected by cablesections, each cable section having pairs of conductors corresponding innumber with the number of said plurality of detectors, characterized byconducting members forming terminal assemblies between each cablesection and a detector, said conducting members, one of each for eachconductor, being circumferentially symmetrically disposed with respectto the axis of each cable section, means for interconnectingcorresponding conducting members of adjacent terminal assemblies, andmeans for connecting each said detector to conductors leading to saidassemblies whereby each said detector may be selectively connected toany pair of said conductors.

2. A seismic surveying apparatus which includes a plurality. ofdetectors each enclosed within a housing and spaced one from the otherand interconnected by cable sections having pairs of conductorscorresponding in number with the number of detectors, the combination ofswitching means for connecting said detectors to selected pairs of saidconductors comprising a plurality of pairs of terminals supported ateach end of each detector housing in sym- -metrical arraycircumferentially of the longitudinal axis thereof, a plurality of pairsof cooperating terminals, one for each pair of conductors,circumferentially symmetrically disposed with respect to thelongitudinal axis of its associated cable section, said symmetricalarrays of terminals providing for electrical contact of said terminalsof one array with those of another in any selected circumferentialposition, means connecting each detector to a pair of terminals at eachend of the housing thereof, means at each detector housing forinterconnecting corresponding terminals at opposite ends thereof, andmeans securing said arrays of terminals in assembled circuit-completingpositions lfor establishing selected electrical circuits which extendVfrom one end of said assembled cable sections to the other.

3. A seismic surveying apparatus in which a plurality of detectors arerespectively separated and electrically interconnected by cablesections, each cable section having pairs of conductors corresponding innumber with the number of said plurality of detectors, characterized byconducting members forming terminal assemblies between each cablesection and a detector, said conducting members, one of each for eachconductor, being disposed at each end of each cable section incooperative array with respect to conducting members associated witheach of said detectors, means for interconnecting correspondingconducting members of said terminal assemblies of each detector, andmeans for connecting each said detector to conductors leading to saidassemblies whereby each said detector may be selectively connected toany pair of said conductors.

4. A seismic surveying apparatus in which a plurality of detectors arerespectively separated and electrically interconnected by cablesections, each cable section having pairs of conductors corresponding innumber with the number of said plurality of detectors, characterized byplug and jack assemblies between each cable section and a detector, saidplugs and jacks, one of each for each conductor, being circumferentiallysymmetrically disposed with respect to the axis of each cable section,means at each detector for interconnecting corresponding elements ofsaid plug and jack assemblies, and means for connecting each saiddetector to conductors leading to said assemblies whereby each saiddetector may be selectively connected to any pair of said conductors.

5. A seismic surveying lapparatus which includes a plurality ofdetectors each enclosed within a housing and spaced one from the otherand interconnected by cable sec-tions having pairs of ccnductorscorresponding in number with the number of detectors, the combination ofswitching means for connecting said detectors to selected pairs of saidconductors comprising a plurality of pairs of jacks supported at eachend of each detector housing in symmetrical array circumferentially ofthe longitudinal axis thereof, electricalconductors extending throughsaid housing and interconnecting said jacks at one end of said housingto corresponding jacks at the opposite end thereof, a plurality of pairsof plugs, one for each pair of conductors, circumferentiallysymmetrically disposed with respect to the longitudinal axis of itsassociated cable section, said symmetrical array of plugs and jacksproviding for insertion of said plugs into said jacks in any selectedcircumferential position, means connecting each detector to a pair ofjacks at each end of the housing thereof, and means securing said jacksand plugs in assembled circuit-completing positions for establishingselected electrical circuits which extend from one end of said assembledcable sections to the other.

6. In a seismic surveying system in which there are provided a pluralityof housings each including a detector, separated by cable sections, eachsaid cable section including pairs of conductors corresponding in numberwith the number of said detectors, and said housings including acorresponding number of pairs oi conductors, the combination of pairs ofjacks and plugs, in number equal to the number of said detectors,respectively carried by said housings and said cable sections, means-forconnecting each detector to corresponding conductors in its associatedhousing, and means for connecting the cable sections to said housings inselectively different angular positions to establish different circuitsfor different detectors, which circuits extend throughout said cablesections and housings for transmission of seismic signals through aplurality of circuits.

7. In a seismic surveying system of the class in which signals from aplurality of seismic detectors are to be recorded either singly orcombined, means for connecting said detectors to desired conductingpaths for transmission of signals to a recorder, comprising a pluralityof multi-conductor cable sections terminated at both ends in a closuremember comprising identical multi-conductor elements, each said elementbeing characterized by pairs of terminals disposed radially andequi-angularly on the face of and symmetrically to the axis of saidelements. a housing for each of said detectors characterized by aplurality of pairs of terminals oriented in cooperative relationshipwith respect to those of said elements, means for fastening each closuremember to a housing in a selected angular position, and means extendingthrough said housing for interconnection of said terminals.

8. A seismic surveying apparatus in which a plurality of detectors arerespectively separated and electrically interconnected by cablesections, each cable section having a plurality of pairs of conductors,characterized by conducting members forming terminal assemblies betweeneach cable section and a detector, said conducting members, one of eachfor each conductor, being circumferentially symmetrically disposed withrespect to the axis of each cable section, means for interconnectingconducting members of adjacent terminal assemblies, and means forconnecting each said detector to conductors leading to said assemblieswhereby each said detector may be selectively connected to any pair ofsaid conductors.

9. A. seismic surveying apparatus which includes a plurality ofdetectors each enclosed within a housing and spaced one from the otherand interconnected by cable sections having a plurality of pairs ofconductors extending therethrough, the combination of switching meansfor connecting selected groups of said detectors to selected pairs ofsaid conductors comprising a plurality of pairs of terminals supportedadjacent each end of each detector housing in symmetrical array about anaxis extending longitudinally of the detector housing, conductorsinterconnecting corresponding terminals at the respective ends of eachhousing, a plurality of pairs of cooperating terminals carried adjacentthe respective ends of each cable section and disposed in likesymmetrical array with those adjacent the end of each said housing,means connecting each detector to a pair of terminals adjacent therespective ends of the housing thereof, the symmetrical arrays of theterminals of said cable sections and of said housing being relativelyrotatable in selection of the pair of conductors to which selecteddetectors are connected, and means securing said cable sections to saidhousings with said arrays of terminals in their selectedcircuit-completing positions for establishing the selected electricalcircuits which extend from one end of the assembled cable sections tothe other.

KENNETH W. MCLOAD.

REFERENCES CITED The following references vare of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,191,120 Slichter Feb. 20, 19402,191,121 Slichter Feb. 20, 1940 2,241,428 Silverman May 13, 19412,329,793 Smith Sept. 21, 1943 2,410,805 Black NOV. 12, 1946 2,423,591Flude July 8, 1947 2,440,903 Massa May 4, 1948 FOREIGN PATENTS NumberCountry Date 367,545 Germany Jan. 23, 1923

